Why is my imported obj not showing up on the grid where I need it to be
This method has always worked for me: 

Firstly, is the origin of the Obj object at the center of the scene (0,0,0)?

If so, skip step 1 and go straight to step 2.


Select the imported obj object whilst in object mode; press Shift+Ctrl+Alt+C. A menu will pop up with a few options - choose Origin to Geometry. (An orange dot should appear near the center of the object).
Press Shift+C to reset the 3D cursor to 0,0,0 (this will change the view but as long as you  don't deselect the imported object this won't be a problem). 
Press Shift+S and select the option Selection to Cursor - which will move the selected object to the center of the scene.


You will probably want to apply the location of the object after this. You may also need to get the origins to match, but that's for a different question and probably has already been answered somewhere.